People boarding planes who cannot switch on their mobile phones or other electronic devices will not be able to take them on flights as part of new security measures, US authorities said last night.
US-bound travellers from Europe and the Middle East have faced tighter airport security in recent days.
Fears have been raised that al-Qaeda-linked militants are developing new explosives that could be taken onto planes undetected.
The checks focused on electronic items such as laptops and mobile phones, fuelling fears that extremists such as al-Qaeda could use them as their latest tactic in a long campaign of attacks involving aircraft.
"During the security examination, officers may also ask that owners power up some devices, including cell phones," the US Transportation Security Administration said in a statement, noting that all electronic devices are screened by security officers.
"Powerless devices will not be permitted on board the aircraft. The traveller may also undergo additional screening," it added.
"TSA will continue to adjust security measures to ensure that travellers are guaranteed the highest levels of aviation security conducted as conveniently as possible."
It was unclear whether the latest measure applied only to travellers at US airports or if people on US-bound flights would also be affected, but the BBC reported that London Heathrow Airport was among non-US airports subject to the new screening rule.